This application is based on and incorporates herein by reference Japanese Patent Application No. 2000-296880 filed on Sep. 28, 2000.
The present invention relates to an automatic vehicle headlight optical axis adjusting apparatus and method for automatically adjusting the illumination area and optical axis of left and right front illumination of headlights provided in a vehicle in conjunction with the steering angle of a steering wheel.
It is proposed to control the left and right swivel of the optical axis of headlights in conjunction with the steering angle of a steering wheel of a vehicle, thereby automatically adjusting the optical axis of the vehicle headlights.
When the road in front in the direction of travel curves to the right with a large radius of curvature and the vehicle is just about to enter the curve as shown in FIG. 8, the inside of the curve (right side in FIG. 8) is outside an illumination area (low beam illumination area) RHA of a right headlight, a main headlight, and is not illuminated. To improve visibility in front of the vehicle, it is therefore desirable to swivel a right swivel light used as an auxiliary headlight so that the inside of the curve is within the area RSA illuminated by the right swivel light. However, this swivel illumination should be provided before the steering angle of the steering wheel is changed. It is therefore not possible to control the swivel of the illumination.
It is also proposed to detect road curvature, etc. from lane markings on the road surface in front of the vehicle in the direction of travel and to control right and left swiveling of the optical axis of the headlights.
However, when the desired swivel angle for swivel control is calculated according to the detected lane markings, etc., erroneous results can occur depending upon, for example, the position of the vehicle relative to the road or lane width, or the road shape.
Various situations are shown in FIGS. 9A and 9B. FIG. 9A shows a right curve in the road to the front in the direction of travel with swivel angle xcex8a based on the white edge line of the right curve, and FIG. 9B shows a straight road in front in the direction of travel with swivel angle xcex8b based on the white edge line of this straight road.
As shown in FIG. 9A, when the road in front of the vehicle curves to the right, swivel angle xcex8a calculated based on the right white edge line existing a specific distance D from the vehicle takes the right curve of the road into account. On the other hand, as shown in FIG. 9B, when the vehicle is on the left side of the lane, angle xcex8b calculated from a right edge line existing the specific distance D from the vehicle is substantially the same as when the road curves right even though the road in front of the vehicle is straight with the same lane width as the curved road in FIG. 9A.
Front visibility can be improved more naturally for the driver by swiveling the optical axis of the headlights when the road in front in the direction of travel curves, and not swiveling the optical axis of the headlights when the road is straight. However, because it is not possible to recognize whether the road curves or is straight, the headlight erroneously swivels the same angle.
It is an object of the present invention to provide an apparatus and method for automatically adjusting an optical axis of vehicle headlights by detecting the curvature of the road etc. in front of the vehicle with good precision based on change in the white edge line, etc. as lane markings while the vehicle is moving, lane markings on the road indicating lane width, to adjustably swivel the optical axis of a vehicle headlight.
According to the present invention, a road in front of a vehicle is detected as curving based on change in position information at at least two different distances of lane markings indicating lane width on a road surface in front of a vehicle before a steering angle of a steering wheel of the vehicle is detected. The optical axis of a vehicle headlight is adjusted to swivel. The optical axis of the headlight is swiveled and adjusted in advance. As a result, if the road in front of the vehicle is detected to curve before a driver turns the steering wheel, the driver""s forward visibility can be improved by first swiveling and adjusting the optical axis of the headlight.